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fix: use explicit spawn context for all multiprocessing primitives #691

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Merged
william-silversmith merged 2 commits into from
Apr 23, 2026
Merged

fix: use explicit spawn context for all multiprocessing primitives #691

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703c4bd
fix: use explicit spawn context for all multiprocessing primitives
dodamih Mar 31, 2026
cd165f9
fix: use ctx.cpu_count and ctx.Process for consistency
dodamih Apr 23, 2026
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21 changes: 10 additions & 11 deletions cloudvolume/datasource/precomputed/image/common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -63,12 +63,16 @@ def parallel_execution(
):
global error_queue

error_queue = mp.Queue()
progress_queue = mp.Queue()
fs_lock = mp.Lock()
# Ensure processes do not accidentally inherit
# locks from forking and deadlock. Instead launch
# new interpreters.
ctx = mp.get_context("spawn")
error_queue = ctx.Queue()
progress_queue = ctx.Queue()
fs_lock = ctx.Lock()

if parallel is True:
parallel = mp.cpu_count()
parallel = ctx.cpu_count()
elif parallel <= 0:
raise ValueError(f"Parallel must be a positive number or boolean (True: all cpus). Got: {parallel}")

Expand Down Expand Up @@ -98,17 +102,12 @@ def cleanup(signum, frame):

try:
if progress:
proc = mp.Process(
target=progress_queue_listener,
proc = ctx.Process(
target=progress_queue_listener,
args=(progress_queue,total,desc)
)
proc.start()

# Ensure processes do not accidentally inherit
# locks from forking and deadlock. Instead launch
# new interpreters.
ctx = mp.get_context("spawn")

with concurrent.futures.ProcessPoolExecutor(
max_workers=parallel,
initializer=initialize_synchronization,
Expand Down